The present invention relates generally to integrated circuit assemblies, and more particularly to assemblies that include one or more integrated circuit dice.
Integrated circuits are typically provided in some type of assembly package. The assembly can protect an integrated circuit from mechanical and/or environmental damage. As electronic devices continue to shrink in size, it can become increasingly desirable to provide packaged integrated circuits that occupy as small an area as possible on a circuit board or the like (have as small a xe2x80x9cfootprintxe2x80x9d as possible).
In most assemblies, conductive paths to an integrated circuit are provided by way of a chip carrier (interposer) that includes a number of xe2x80x9cleads.xe2x80x9d The various leads of an integrated circuit can be then be connected to each other on a circuit board by traces. For some applications, the impedance presented by such traces can limit signal propagation speeds, require undesirably high drive current, and/or consume more power than desired. Along these same lines, many types of packages, due to bond wires and/or traces, may introduce unwanted inductance along a signal path. Such inductance can lead to xe2x80x9cground bouncexe2x80x9d (unwanted fluctuations in a ground potential when current flows through a signal path) or other undesirable results.
It can also be desirable to provide as many circuit functions as possible in the same assembly. However, integrating multiple types of circuits within a single semiconductor substrate can be prohibitively expensive and/or add complexity to a manufacturing process.
One way to address the above concerns is to provide assemblies that include more than one integrated circuit device (xe2x80x9cchip or diexe2x80x9d). A number of conventional multi-chip assemblies will now be described.
FIGS. 8A and 8B show a first conventional multi-chip assembly 800. FIG. 8A shows a top plan view of a multi-chip assembly 800. A multi-chip assembly may be a ball grid array (BGA) assembly that includes multiple dice 802-0 to 802-2 situated side-by-side on an assembly substrate 804. Each die (802-0 to 802-2) may be connected to a substrate 804 by a conventional wire bond arrangement. An exemplary bond wire is indicated by the reference character 806, and may connect a bond pad on a die (802-0 to 802-2) to a conductive trace (not shown in FIG. 8A) on a substrate 804.
Various conductive traces on substrate 804 may connect various dice (802-0 to 802-2) to one another. Substrate traces may also provide a conductive path to solder balls (not shown in FIG. 8A) formed on a bottom of a substrate 804.
FIG. 8B shows a side cross-sectional view of an assembly 800. One end of a bond wire 806 can be connected to a bond pad 808 on a die 802-0. Another end of bond wire 806 can be connected to trace 810 on substrate 804. A die 802-0 can be connected to a substrate 804 by a die attach 812. As noted above, a trace 810 may provide a conductive path to solder balls 814 situated on an assembly bottom. Solder balls 814 may provide a BGA type connection for the multi-chip assembly 800.
A multi-chip approach such as that set forth in FIG. 8A and 8B can provide multiple functions without having to form a larger integrated circuit. Such an approach may also provide some reduction in the footprint presented by the various chips (802-0 to 802-2) as traces formed on a substrate 804 may be shorter than traces of a circuit board. Shorter traces on a substrate 804 may require less current to drive and present smaller impedance than conventional circuit board traces.
A second conventional approach is shown in FIGS. 9A and 9B. FIG. 9A is a top plan view of a multi-chip assembly 900 according to another conventional example. A multi-chip assembly 900, like the example of FIGS. 8A and 8B, can include dice 902-0 to 902-2 arranged in a side-by-side fashion. Unlike the example of FIGS. 8A and 8B, dice 902-0 to 902-2 may be connected to a substrate 904 by conductive bumps (e.g., in a xe2x80x9cflip-chipxe2x80x9d fashion). In a flip-chip arrangement, a die can include a bonding surface that faces an assembly substrate 904. A number of connections can be provided between a bonding surface and traces in a substrate 904 by conductive structures such as bumps, or the like. Conductive connections between dice (902-0 to 902-2) and a substrate 904 are shown as dashed circles. One of the many connections is shown as item 906. Like the arrangement of FIGS. 8A and 8B, various conductive traces (not shown) on a substrate 904 may connect various dice (902-0 to 902-2) to one another, and to solder balls (not shown in FIG. 9A) formed on a bottom of a multi-chip assembly 900.
FIG. 9B shows a side cross-sectional view of an assembly 900. A number of conductive connections 906 may exist between a die 902-0 and an assembly substrate 904. Solder balls 908 may provide a BGA type connection for a multi-chip assembly 900.
As in the case of the example of FIGS. 8A and 8B, a multi-chip approach such as that set forth in FIG. 9A and 9B can provide multiple functions. A multi-chip assembly 900 may also have a smaller footprint than a multi-chip assembly 800, as bond wire connections may require more area around the periphery of dice 802-0 to 802-2 than flip-chip type connections.
A drawback to the arrangements of FIGS. 8A, 8B, 9A and 9B is that an assembly footprint may be no smaller than the combined area of the dice contained within the assembly.
A third conventional example is shown in FIG. 10. FIG. 10 shows a side cross-sectional view of multi-chip assembly 1000. A multi-chip assembly 1000 may include dice 1002-0 and 1002-1 that are stacked one on top of the other. Die 1002-0 can be situated on an assembly substrate 1004, while die 1002-1 can be situated on die 1002-0. Lower bond wires, one of which is shown as item 1006, can connect die 1002-0 to traces on a substrate 1004. Higher bond wires, one of which is shown as 1008, can connect die 1002-1 to traces on a substrate 1004. Higher bond wires 1008 can extend over lower bond wires 1006. Like the previously described examples, traces (not shown) on a substrate 1004 may connect dice 1002-0 to 1002-1 to one another and/or to solder balls 1010 formed on a bottom of a substrate 1004.
A multi-chip packaging arrangement such as that shown in FIG. 10 can provide multiple functions without having to form a larger integrated circuit. Such a multi-chip assembly 1000 can also provide a smaller footprint than the previously described examples, as the dice (1002-0 and 1002-1) may be stacked on top of one another, and not arranged in a side-by-side fashion. Traces on substrate 1004 can present smaller impedance than circuit board traces.
A drawback to the arrangement of FIG. 10 arises out of a ratio between the sizes of the dice in the assembly. In particular, a top die may have to be smaller than a bottom die to allow bonding from a substrate to a bottom die. Further, a substrate may have to include sufficient area to allow upper bond wires to be formed over lower bond wires.
Yet another conventional example of a multi-chip assembly is shown in FIG. 11 in a cross-sectional view. A multi-chip assembly 1100 may include multiple dice (1102-0 to 1102-2) having traces that extend from bond locations on a die surface to a die edge. Vertical traces may connect traces on dice edges to one another, and to solder balls 1104 on a bottom of an assembly 1100. Connections may include gold traces insulated by a dielectric such as polyimide. In addition, or alternatively, connections may be made by xe2x80x9cflex tapexe2x80x9d which can include a flexible insulating tape having conductive traces formed within.
A multi-chip packaging arrangement such as that shown in FIG. 11 can provide multiple functions, and a comparatively small footprint with respect to the other described conventional examples. Traces formed by polyimide-gold and/or flex tape connections may present smaller impedance than circuit board traces. In addition, unlike multi-chip assembly 1000, multi-chip assembly 1100 may not be subject to die size ratios, as in the case of assembly 1000 of FIG. 10.
Other variations on a stacked arrangement, such as that of FIG. 11, may include attaching a number of dice in a row to a flex tape having chip carrier structures. A stacked chip arrangement can then be created by folding such a flex tape in an accordion like fashion.
A drawback to stacked die assemblies, such as that shown in FIG. 11, can be the complexity and costs involved in forming such an assembly.
It would be desirable to arrive at some way of forming a multi-chip assembly that provides a small footprint relative to conventional approaches, but that does not suffer from the complexity and/or the cost of conventional stacked die assemblies.
The present invention may include an assembly for multiple integrated circuits in die form. An assembly may include a substrate having a recessed portion and a raised portion. An assembly may further include a first die having a plurality of conductive connections to a recessed portion. In addition, at least a second die can have a portion that overlaps a first die. A second die may also include a plurality of conductive connections to a raised portion of a substrate.
According to one aspect of the embodiments, a recessed portion of a substrate may be surrounded by a raised portion of a substrate to form a cavity that can contain a first die.
According to another aspect of the embodiments, a first die may have a flip-chip type connection to a recessed portion of a substrate.
According to another aspect of the embodiments, a second die that overlaps a first die may have a flip-chip type connection to a raised portion of a substrate.
According to another aspect of the embodiments, a second die that overlaps a first die may have a wire bond connection to a raised portion of a substrate.
According to another aspect of the embodiments, a first die can have a plurality of conductive connections to a recessed portion while a number of other dice may overlap a first die. Such other multiple dice may have a plurality of conductive connections to a raised portion of a substrate.
According to another aspect of the embodiments, a first die may have a connection to traces on a recessed portion of a substrate. Traces on a recessed portion can provide a conductive path to traces on a raised portion of a substrate. In addition, or alternatively, traces on a substrate may provide a conductive path to assembly connections. Assembly connections include solder balls, pins, and/or conductive leads, as but a few examples.